Ganged potentiometers



Feb. 7, 1961 w. w. LYON 2, 71, 74

GANGED POTENTIOMETERS Filed Sept. 8, 1959 2 Sheets-Sheet 1 all INVENTOR BY WrW ATTORNEYS Feb. 7, 1961 w. w. LYON 2,971,174

GANGED POTENTIOMETERS Filed Sept. 8, 1959 2 Sheets-Sheet 2 INV EN TOR Willie; Mzyom ATTORNEY5 2,971,174 GANGED POTENTIOMETERS William W. Lyon Lexington Mass. Electronic Associates,

Inc, a corporation of Massachusetts The present invention relates to ganged potentiometers, and particularly to the relative phasing of ganged potentiometers.

In numerous electronic and electrical systems it is necessary to apply different voltage functions, todifferent circuits or components of the system. Further, it is frequently necessary to apply these difierent functions in a related manner. For many purposes, each of the functions may be readily embodied in the winding or resistance unit of a potentiometer or rheostat, and it is therefore a common expedient to gang the various function potentiometers into a single unit, operated in unison by a common drive shaft. Thus, once the potentiometer units of the ganged assembly are properly phased with each other, the output functions of all of the units are properly related in the required manner. The ganged units are locked in this phased relationship, and unison rotation of the wiper arms by a common drive shaft obtains an output function for each potentiometer or rheostat at all times properly phased in the desired relation to the output function of each of the other potentiometers or rheostats.

Considering rotary type potentiometers, it is common to gang such units along the wiper arm drive shaft axis, and use a common shaft, or axially connected shafts, for driving each of the wiper arms. However, the precise phasing of a series of such ganged potentiometers is not an easy task, because it is necessary to obtain a precise relative position of the wiper contact and resistor of each unit with respect to every other unit. It is the common practice to assemble and phase a desired gang of potentiometers at the factory and deliver the gang as a unit. Thereafter, if for any reason it becomes necessary to replace one of the units of the gang, it has in many instances been necessary to return the whole gang to the factory, in order that the unit may be replaced and properly phased with the other potentiometer units in the gang.

In accordance with the present invention, however, each potentiometer unit to be employed in a gang is, when manufactured, phased with respect to a common reference, and each such referenced unit is so constructed that it can be thereafter readily ganged with other similarly referenced units in the phased relationship to which it has been referenced.

Generally, the present invention provides for each potentiometer unit a resistance element, a variable contact and wiper arm, and a rotationally mounted shaft. The wiper arm and its variable contact are carried by the shaft so that the contact traverses the resistance element on rotation of the shaft. These units are designed to be ganged along the axis of the wiper shaft. In ganging, the shafts of two adjacent units are designed to interlock for unison rotation, and the interlock provides only one relative angular position at which the two shafts can interlock. Thus, the shafts are automatically phased to each other in a predetermined relationship. The resistance unit which circumscribes an are or circle about the shaft, is usually fixedly mounted in a casing, and means are norassignor to Ace 2,971,174 Patented Felo. 7, 1961 Bee mally provided for interrelating the rotational position of two adjacent casings into a predetermined relationship. Thus, upon gauging two units, the relative shaft positions and relative resistance unit positions are both directed into a predetermined angular relationship. The wiper arm is designed to be mounted on the shaft in any desired angular position, and to be readily anchored in a desired adjusted angular position. Since the casings and shafts of all the units are adapted to occupy a known fixed rotational relationship to each other, there remains merely to locate and anchor the wiper arm of each unit in that position on the shaft which establishes the desired phase relationship of the variable contacts of the several units with their respective resistance units. Once this is done, the several units can be readily ganged, and they will be constrained at all times to occupy that relationship which provides the desired phasing of their output functions upon rotation of their interlocked shafts.

Since the constrained relationship of the casings and shafts of the several units constitutes a fixed relationship of each unit to a common reference, it is apparent that at any time new potentiometer units may be manufactured for replacement of a ganged unit or addition to a gang of units. These new units may be properly phased to said common reference and then delivered for easy field installation in an existing gang of potentiometers, without the necessity of returning the whole gang to the factory.

Accordingly, it is one object of the present invention to provide rotary potentiometers adapted to be ganged in a predetermined relative relationship.

Another object of the present invention is to provide rotary potentiometers having wiper arm shafts adapted to be axially interlocked in only one relative angular relationship.

And another object of the present invention is to provide a rotary potentiometer having a wiper arm adapted to be anchored in any desired angular relationship upon the wiper arm control shaft.

Other objects and advantages of the present invention will become apparent to those skilled in the art, from a consideration of the following detailed description of one exemplary specific embodiment of the invention, had in conjunction with the accompanying drawings, in which like numerals refer to like or corresponding parts, and wherein:

Fig. l is a plan view of a plurality of ganged rotary potentiometers;

Fig. 2 is a partial and enlarged longitudinal section of the ganged potentiometers, taken along line 22 of Fig. 1;

Fig. 3 is an end view into the casing of one of the potentiometers of Figs. 1 and 2, with the wiper arm and shaft removed;

Fig. 4 is a detailed showing of the wiper arm of the present invention, as viewed from one face;

i Fig. 5 is a detailed showing of the wiper arm of the present invention, as viewed from the other face;

Fig. 6 is an isometric view of the wiper arm shaft; and

Fig. 7 is a cross-sectional view of an assembled potentiometer unit, taken along line 7-7 of Fig. 2.

In accordance with the present invention, a plurality of rotary potentiometer units 10 are axially ganged together, and held in assembled relationship by means of clamping bands 12 adapted to cooperate with the shoulders 12a on the adjacent exterior portions of the potentiometer casings 15, to hold the several units in assembled, ganged association. Adjacent end surfaces of the ganged casings or cups 15 are matingly stepped at 26 and 27 to provide a desired interlocking seal between adjacent cups. The rotary wiper arm shaft 11 provides a common drive for each potentiometer wiper arm, composed of a separate shaft 50 for each potentiometer unit appropriately axially interlocked, as will be more fully explained hereinafter.

As best shown in FigsZ and 3, each'potentiometer casing 15 is. substantially cup shaped, and is designed in general to house and support a resistance element, which may be in the form of a wire mound resistance card 16, a variable wiper arm and contact 70, a slip ring contact wire 19 for obtaining the voltage tapped from the resistance element by the wiper arm contact, and a terminal board 13 for effecting electrical connection with the elements of the potentiometer. In greater detail, the cup or housing 15 is preferably formed of metal, and the resistance card 16 is disposed oircumferentially around the interior surface of the side wall 15a of the cupped housing. An insulator ring 17 is disposed between the resistance element 16 and housing 15 in order to prevent the housing from short circuiting the resistance element. The end Wall 1512 of the housing is provided with a central aperture 15c, around which an internally projecting annular flange 15d is formed. Flange 15d provides a seat for reception of an annular split tap ring 18 of insulation material. This tap ring has two functions: one, to support the slip ring contact wire 19; and the other, to sup port any desired number of fixed taps, such as 20 soldered at 21 to a selected point on resistance unit 16. The tap 2,0 and slip ring contact 19 are hairpin shaped wires passing through the flange on the tap ring, and being secured thereto by a spot of suitable cement or resin. A terminal board 13, carrying terminal pins 14 is mounted on the outside surface of the cupped housing 15. Leads 22 from the tap 20, 23 from the slip ring contact 19, and 24 and 25 from the ends of the resistance element 16, pass through an aperture 152 in the housing to the underside of the terminal board, and there pass through hollow pins 14, and are trimmed and soldered to the pins at 14a.

A shaft 50 is rotationally mounted and supported coaxially within the cupped housing 15 by means of a bearing generally indicated by the numeral 60. Shaft 50 is adapted to carry and support the wiper arm and variable contact assembly generally indicated by the numeral '70. This assembly comprises a clamping plate 31 mounting a contact carrier and slip ring plate 29. These two plates are electrically insulated from each other by interposed insulator plate 31}. The three plates 29, 30, and 31 are retained in assembled condition by a pair of rivets or eyelets 32 provided with appropriate insulation bushings 33 to. keep clamping plate 31 electrically isolated from the contact plate 29.

One end of contact plate 29 is formed with a flange or shelf 39, upon which is mounted an appropriate spring wiper contact finger 28 adapted to traverse the resistance element 16.. The other end of contact plate 29 is formed with the slip ring or collector ring 41, having a circumferential groove 41a: for receiving and guiding the spring contact wires 19. Clamping plate 3 1 is formed with a serrated aperture 34 adapted to receive and circumferentially clamp upon shaft 50. The plate 31 is formed so that the aperture 34 can be enlarged sufiiciently to per rnit positioning of the plate on the shaft, and thereupon released to clamp about the shaft in response to. the spring action of the clamp-ing plate material. To this end, the plate 31 is slotted at 35 from the aperture 34 to the bottom of the plate, and is slotted at 37 upwardly a short distance from aperture 34. The upper slot terminates in an enlarged cut out 38 forming a key-hole slot to facilitate resilient spreading of the legs forming the two sides of the aperture 34. Notches 36 are formed close to the bottom end of aperture 35 for reception of a spreading tool. The insulating plate 30 and contact plate 29 are apertured to correspond with the aperture 34, and in the contact plate 29, the slip ring 41 circumscribes this aperture. Insulating plate 30 is further apertured to correspond with the spreading tool notches 36. An insulating bushing 42, which may conveniently be in a single orientation.

formed integrally with the insulation plate 30, lines the inside circumference of the aperture through the contact plate to isolate the contact plate from the shaft 50.

The shaft 50 is adapted to be positioned within the clamping plate aperture 34 and the bushing 42, and to be rotationally supported within the housing cup 15 by means of bearing 60. This shaft is provided at one end with an axially protruding spline 51, and at the other end with an axially oriented spline receiving slot 52. The

spline and the slot are correspondingly located on the opposite ends of the shaft, and are both equally off axial center in mirror image relation. Thus, taking two shafts 50, the spline 51 of one can be coupled into the slot 52 of the other in two relative positions of the shafts, said two positions being angularly displaced by However, because of the OE center arrangement of the spline and slot, these two shafts can be coupled in only one relative angular position which will place the shafts in coaxial alignment. spline 51 and spline slot 52 have no more than one plane of symmetry through the axis of the shaft 50.

Thus, in practicing the present invention, a Wiper arm is mounted on a shaft 50 by spreading the legs of the clamping plate 31, and its angular position on the shaft is adjusted at will. When released, the spring force of the wiper arm legs securely clamp the wiper arm assembly in a selected angular position on the shaft. The shaft 50, its bearing structure 60, and the cup 15 (already housing the resistance element 16, the tap ring 18, and the terminal board 13) are assembled to form the unit shown in Figs. 2 and 7, with the slip ring contact wire 19 riding in the groove 41a of the slip ring 41. The wiper arm 70 is placed in an adjusted angular position on shaft 50, so as to locate the contact element 28 at a desired point on resistance element 16 when the shaft 50 and housing 15 occupy a prescribedor selected angular relationship to each other. For purposes of reference, this position of the wiper contact is termed the zero position. It is apparent, that any number of potentiometers may be similarly zeroed by setting the wiper contact at the appropriate zero point on the resistance element with the casing 15 and shaft 50 occupy the same prescribed or selected angular relationship to each other. When a plurality of such correspondingly zeroed potentiometers are axially ganged in a manner as indicated in Figs. 1 and 2, the mating off-axial-center splines and spline grooves cause the successive shafts all to be placed When the casings are brought into corresponding angular orientation, all the wiper contacts of the gang are in phase with each other with respect to their zero position. It is apparent that at any time any potentiometer unit of the gang can be readily replaced, or an additional unit added, and such new unit will be readily phased with the existing units, provided it has been originally zeroed with reference to the same relative orientation between the shaft and casing as the units existing in the gang. The new unit is inserted and phased with the others merely by interlocking its shaft with the adjacent shafts, and adjusting its casing into correspondence with the other casings.

In the foregoing assembly operations, the casings may be brought into corresponding angular positions by means of any reference device, such as by applying a reference mark on a corresponding point of each casing, which may be readily alined to bring the casings into correspondence. However, it is deemed sufficient that the initial phasing be a rough or approximate operation, wherein the approximate alignment of the terminal boards 13 would be sufficient. Thereafter, the assembled shafts 50 are held in position, and with the potentiometers connected in an electrical circuit, the casings are separately angularly adjusted relative to their shafts and wiper contacts, until the electrical outputs of each unit are ob-. servedto be in exactphase relationship.- The units "are This relationship exists because the then clamped together by bands 12. This electrical in situ phasing can effect a more accurate relationship than a mechanically prescribed position for the casing. Therefore, it is preferred to utilize mechanically prescribed relative positions for the casings as a first approximation of phasing, followed by the instant electrical phasing procedure for the final adjustment.

Having thus described one specific embodiment of the present invention, it is understood that this is done for purposes of illustration only in order to facilitate a complete understanding of the invention. Accordingly, the invention is not limited to the specific structure of this embodiment, and such changes, variations, and modifications as are embraced by the spirit and scope of the appended claims are contemplated as within the purvue of this invention.

What is claimed is:

1. A gang of rotary potentiometers comprising at least two potentiometer units, each unit comprising a casing element, a shaft element rotatively supported by said casing element, a resistance member carried by one of said elements, a variable tap member carried by the other of said elements for traversing said resistance member on relative rotation of said elements, means for adjustably clamping one of said members to the element by which it is carried, and means on the ends of said shaft elements of both units for axially coupling the two shaft elements for unison rotational movement, comprising an axial extending spline on one end of one of said shaft elements located oif axial center and a mating spline slot on one end of the other of said shaft elements in a position corresponding to that of said spline, to permit coaxial coupling of said two shaft elements in only one relative angular orientation.

2. A gang of rotary potentiometers as set forth in claim 1, wherein said clamping means comprises a bifurcated element of resilient material having a pair of opposed serrated jaws adapted to grip the element by which the tap member is carried.

3. A gang of rotary potentiometers as set forth in claim 1, and further including means for indexing the casing elements into a predetermined relative angular orientation.

4. In a rotary potentiometer comprising a casing, a resistance element carried by said casing, a shaft rotatively supported by said casing, and a variable tap structure carried by said shaft for traversing said element on rotation of said shaft, the improvement wherein said variable tap structure comprises a wiper member enga ing said element, a conductive carrier mounting said wiper member, a collector means on said carrier, contact means slidably engaging said collector means electrically connecting said wiper member to a terminal, a bifurcated resilient metallic clamping means mounting said carrier, said clamping means being mounted on said shaft, and means electrically insulating said clamping means from said carrier.

5. In a rotary potentiometer as set forth in claim 4, said bifurcated clamping means having a serrated area adapted to surround and bite said shaft.

6. In a potentiometer as set forth in claim 5, said bifurcated clamping means further including an area in each leg adapted to cooperate with a spreading tool for resiliently spreading said legs to facilitate applying and adjusting said clamping means to said shaft.

7. in a potentiometer as set forth in claim 6, said bifurcated clamping means including a key-hole slot on the opposite side of said serrated area from said area adapted to cooperate with a spreading tool, to reduce the force necessary for spreading said legs.

8. A rotary potentiometer unit adapted to be ganged with mating potentiometer units for unison rotational adjustment, comprising a casing element, a shaft element rotatively supported by said casing element, a resistance member carried by one of said elements, a variable tap member carried by the other of said elements for traversing said resistance member on relative rotation of said elements, means for adjustably clamping one of said members to the element by which it is carried, first coupling means including a projecting element extending from one end of said shaft element having no more than one plane of symmetry through the axis of said shaft element, and second coupling means including a socket formed in the other end of said shaft element having no more than one plane of symmetry through the axis of said shaft element and having a mating configuration with respect to the configuration of the first coupling means, said two coupling means being correspondingly located on said shaft, whereby the shafts of a plurality of such potentiometers can be coaxially coupled in only one relative angular orientation.

9. A rotary potentiometer unit as set forth in claim 8, wherein said projecting element extends parallel to the axis of said shaft element and is located off the axial center of said shaft element, and said socket is formed parallel to the axis of said shaft element and is located ofi the axial center of said shaft element.

10. A rotary potentiometer unit as set forth in claim 9, wherein said projecting element is a spline, and said socket is a spline slot.

References Cited in the file of this patent UNITED STATES PATENTS 2,543,228 Burgess Feb. 27, 1951 2,676,226 Mucher Apr. 20, 1954 2,811,620 Mucher et a1 Oct. 29, 1957 2,859,319 Karg Nov. 4, 1958 2,883,500 Budd et al Apr. 21, 1959 2,898,567 Drewitz et al. Aug. 4, 1959 2,908,882 Gottschall et a1 Oct. 13, 1959 

